Multidimensionales Verfahren zur Bestimmung des Regelleistungsbedarfes unter Berücksichtigung von Unsicherheiten

One of the most crucial constraints in operation of electrical power supply systems is the permanent balance between generation and load. Reserve power is held ready to be able to keep this balance also in case of the occurrence of unpredictable events like power plant outages or inevitable deviations of power injections from their predicted values. At this, the allocation of operating reserves is in the field of conflict between level of reliability and cost effectiveness. The amount of reserve generation capacity required in a control area heavily depends on prediction quality which constitutes the need for high quality predictions. This article is about the influence of prediction quality on the amount of reserve generation capacity required in a control area. The algorithms for the assessment of required reserve generation capacity known from literature use the variation calculus technique to account for the aforementioned unpredictable events and prediction errors. In this article, an extension to a convolution-based method is presented in which the uncertainties of the predictions are expressed using intervals. Each parameter is represented by an independent dimension, assuming statistical independence among them. This allows the distinct analysis of each parameter’s influence on the amount of required reserve generation capacity. In addition, two methods for the visualization of the multi-dimensional results are presented, allowing a comprehensive analysis of the parameters’ influences. Standard distribution functions are used to represent the parameters for the simulation and the results are shown as probability density functions of possible imbalances. Based on forecasts of the development of conventional power plants and regenerative generation in the years 2020, 2030 and 2040, the required control power of the future German transmission system is calculated. Influences and dependencies are identified with the extended convolution-based method.     

Partnerships and the private recruitment industry

This article, based on a postal survey and qualitative interview‐based research, examines the relationship between major private recruitment bureaux and their clients in the UK, with particular attention to the recruitment and selection of temporary workers. The private recruitment industry is growing and large bureaux are seeking closer partnership arrangements with clients. Contracts for labour services are being developed on a 'preferred' supplier basis – similar in type to the approach taken for the purchase or supply of goods or components. However, formal preferred supplier contracts with temporary work bureaux were used by only a minority of clients, usually larger organisations or those having projects or workplaces with high volume demand. While such bureaux seek models of relational contracting or partnering, many clients prefer less fully engaged or 'semi‐distanced' relations facilitated by the informal dimensions of inter‐organisational contacts.     

R-estimation of the parameters of a multiple regression model with measurement errors

We consider the theory of R-estimation of the regression parameters of a multiple regression models with measurement errors. Using the standard linear rank statistics, R-estimators are defined and their asymptotic properties are studied as robust alternatives to the least squares estimator. This paper fills the gap of the rank theory for the estimation of regression parameters with measurement error models. Some simulation results are presented to show the effectiveness of the R-estimators.     

Technology assessment network building: The International Association of Technology Assessment and Forecasting Institutions

With the globalization of trade and the increased understanding of transboundary problems such as global climate change, the need for understanding the consequences of technological change has never been higher. Institutional arrangements necessary to assess these changes and make decision makers aware of the consequences have not necessarily adapted to these world conditions. In response to this leading technology assessment and forecasting institutions formed an international association of technology assessment and forecasting institutions to assist in the diffusion of technology assessment in the decision-making process. This paper discusses the origins of the International Association of Technology Assessment and Forecasting Institutions (IATAFI) and the goals and vision for the organization. The following articles represent some of the topics discussed at the first IATAFI conference in Bergen, Norway in May 1994.     

Consequences of competitive bidding in project-based production

This paper discusses the consequences competitive bidding have on lead time in project-based production, such as construction. Earlier studies argued that competitive bidding may significantly increase resource consumption and generate waste in the delivery process, which this paper supports. However, the relation between competitive bidding and lead time has been less discussed. Lead time reduction has long been considered a fundamental objective for overall business improvement. An objective of our study was to understand what contributes to long lead times. The reported findings are from a 4-year study on the delivery process of power distribution equipment, a type of engineered-to-order (ETO) product. The paper concludes by suggesting procurement practices that reduce lead times for ETO products.     

How interethnic marriages affect the educational attainment of children: Evidence from a natural experiment

The allocation of Moluccan immigrants across towns and villages at arrival in the Netherlands and the subsequent formation of interethnic marriages resemble a natural experiment. The exogenous variation in marriage formation allows us to estimate the causal effect of interethnic marriages on the educational attainment of children from such marriages. We find that children from Moluccan fathers and native mothers have a higher educational attainment than children from ethnic homogeneous Moluccan couples or children from a Moluccan mother and a native father.     

What makes a good conference? Analysing the preferences of labour economists

Conferences are an important element in the work of researchers, requiring substantial investments in fees, travel expenses and the time spent by the participants. The aim of this paper is to identify the preferences of participants with respect to conference characteristics. Based on a sample of European labour economists, preferences are measured using the vignette approach where participants are asked to choose between hypothetical European Association of Labour Economists (EALE) conferences. We find that the keynote speakers are the most important element in the preference for a conference, followed by the location of the conference. There is substantial heterogeneity in the taste of labour economists especially with respect to location, though the link between preference parameters and measured characteristics like gender, age and seniority is limited. Factor analysis suggests that the variety in preferences can be best described by a latent variable that reflects the weights people put on content versus fun.     

Critical success factors for managing purchasing groups

In this article, we identify critical success factors for managing small and intensive purchasing groups by comparing successful and unsuccessful purchasing groups in a large-scale survey. The analysis of our data set suggests the following success factors: no enforced participation, sufficient total contribution of efforts, all members contribute with knowledge, continuity in member representation, communication, and fair allocation of savings. The findings suggest among other things that it is important that after a voluntary decision has been taken to cooperate, the members need to show that they are committed. Other factors such as interorganisational trust and formal structures are important when establishing interorganisational cooperation, but should otherwise be considered as necessary yet not sufficient in the management phase of a successful purchasing group.     

Concept‐Based Bayesian Model Averaging and Growth Empirics

In specifying a regression equation, we need to specify which regressors to include, but also how these regressors are measured. This gives rise to two levels of uncertainty: concepts (level 1) and measurements within each concept (level 2). In this paper we propose a hierarchical weighted least squares (HWALS) method to address these uncertainties. We examine the effects of different growth determinants taking explicit account of the measurement problem in the growth regressions. We find that estimates produced by HWALS provide intuitive and robust explanations. We also consider approximation techniques which are useful when the number of variables is large or when computing time is limited.